Midsole system with graded response

ABSTRACT

A sole structure for an article of footwear comprises a midsole system with a plurality of cushioning units, each having multiple cushioning layers configured to work together as a system to absorb a compressive load, such as a dynamic compressive load due to impact with the ground, in stages of progressive cushioning according to the relative stiffness values of the layers. Various midsole systems disclosed include isolated cushioning units, linked cushioning units, sole layers having stanchions interfacing with the midsole system, midsole systems with sole layers having keyed and unkeyed portions overlying a bladder, and midsole systems with vertically-stacked cushioning units disposed in inverted relationship to one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/510,002 filed May 23, 2017, which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present teachings generally include a sole structure for an articleof footwear including a midsole system.

BACKGROUND

An article of footwear typically includes a sole structure configured tobe located under a wearer's foot to space the foot away from the ground.Sole structures in athletic footwear are typically configured to providecushioning, motion control, and/or resilience.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration in side view of an article offootwear having a sole structure with a midsole system that has multiplecushioning units.

FIG. 2 is a schematic illustration in cross-sectional perspective viewof a portion of the sole structure of the article of footwear of FIG. 1taken at lines 2-2 in FIG. 1 showing one of the cushioning units.

FIG. 3 is a schematic illustration in cross-sectional perspective viewof a portion of an alternative cushioning unit for the article offootwear of FIG. 1.

FIG. 4 is a schematic illustration in cross-sectional view of theportion of the sole structure of FIG. 2 showing a third cushioninglayer.

FIG. 5 is a schematic illustration in cross-sectional view of theportion of the sole structure of FIG. 4 in a first stage of compression.

FIG. 6 is a schematic illustration in cross-sectional view of theportion of the sole structure of FIGS. 4-5 in a second stage ofcompression.

FIG. 7 is a schematic illustration in cross-sectional view of theportion of the sole structure of FIGS. 4-6 in a third stage ofcompression.

FIG. 8 is a plot of force versus displacement during dynamic compressiveloading of the portion of the sole structure of FIG. 2.

FIG. 9 is a schematic illustration in bottom view of the midsole systemof the article of footwear of FIG. 1.

FIG. 10 is a schematic illustration in bottom view of an embodiment of athird cushioning layer for a midsole system.

FIG. 11 is a schematic plan view illustration of an embodiment of amidsole system with a group of fluidly-interconnected cushioning units.

FIG. 12 is a schematic perspective illustration of the midsole system ofFIG. 11 in an inverted position.

FIG. 13 is a schematic plan view illustration of an embodiment of amidsole system with a group of fluidly-interconnected cushioning unitsand linking chambers.

FIG. 14 is a schematic illustration of the midsole system of FIG. 13 inbottom view.

FIG. 15 is a schematic perspective and fragmentary illustration of themidsole system of FIGS. 13-14.

FIG. 16 is a schematic cross-sectional illustration of the midsolesystem of FIG. 13 taken at lines 16-16 in FIG. 13.

FIG. 17 is a schematic illustration in bottom view of a sole structurewith an embodiment of a midsole system.

FIG. 18 is a schematic cross-sectional illustration of a sole structurewith an embodiment of a midsole system and taken at lines 18-18 in FIG.20.

FIG. 19 is a schematic cross-sectional illustration of the solestructure of FIG. 18 taken at lines 19-19 in FIG. 18.

FIG. 20 is a schematic illustration in bottom view of a sole structurewith an embodiment of a midsole system.

FIG. 21 is a plot of force versus displacement during dynamiccompressive loading of the heel portion of the sole structure of FIG.18.

FIG. 22 is a plot of force versus displacement during dynamiccompressive loading of the midsole portion of the sole structure of FIG.18.

FIG. 23 is a plot of force versus displacement during dynamiccompressive loading of the forefoot portion of the sole structure ofFIG. 18.

FIG. 24 is a schematic perspective illustration of a bottom surface of asole layer of a midsole system of FIG. 25

FIG. 25 is a schematic cross-sectional illustration of an embodiment ofan article of footwear having a sole structure with a midsole system inan unloaded state.

FIG. 26 is a schematic cross-sectional illustration of the article offootwear of FIG. 25 with the sole structure under compressive loading.

FIG. 27 is a schematic cross-sectional illustration of an embodiment ofa midsole system for an article of footwear.

FIG. 28 is a schematic cross-sectional illustration of an embodiment ofa midsole system for an article of footwear.

FIG. 29 is a schematic plan view illustration of a first polymeric sheetfor a midsole system showing a pattern of anti-weld material.

FIG. 30 is a schematic plan view illustration of a second polymericsheet for a midsole system showing a pattern of anti-weld material.

FIG. 31 is a schematic plan view illustration of a third polymeric sheetfor a midsole system showing a pattern of anti-weld material.

DESCRIPTION

Various footwear sole structures with midsole systems are disclosed,each with multiple cushioning layers configured to work together as asystem to absorb a compressive load, such as a dynamic compressive loaddue to impact with the ground, in stages of progressive cushioning(referred to as staged or graded cushioning) according to the relativestiffness values of the layers. Underfoot loads are “dosed” or “staged”to the wearer, with each stage having a different effective stiffness.The progressive cushioning may be correlated with different regions ofthe sole structure, such as by providing an initial stiffness responsein the heel region at heel impact, with a stiffness that increases asthe foot moves forward to toe-off at the forefoot region. For example,the sole structure may provide first, second and third stages ofcompression, in order, each providing a different stiffness, with thethird stage being the stiffest. Because the third stage of compressionoccurs after the first and second stages, it may coincide with movementof the article of footwear to a dorsiflexed position in which the weareris near a final toe-off.

The cushioning response is therefore staged not only in relation toabsorption of the initial impact force, but also in relation to theforward roll of the foot from heel to toe. In one example, the midsolesystem initially provides a low, linear rate of change of load todisplacement (i.e., compressive stiffness), followed by a higher,possibly nonlinear rate, and then a more rapid, exponentially increasingrate. The sole structure provides the graded cushioning while beinglightweight and flexible. Moreover, various embodiments may exhibit anunloading behavior (i.e., behavior when the dynamic compressive force isremoved) that provides significant energy return.

In one or more embodiments, a sole structure includes a midsole systemthat has multiple cushioning units, each with multiple cushioning layersof sealed chambers containing gas. Each cushioning unit includes a firstcushioning layer comprising a first sealed chamber, and a secondcushioning layer comprising a second sealed chamber. The first sealedchamber and the second sealed chamber each retain gas in isolation fromone another. The first cushioning layer underlies the second cushioninglayer and has a domed lower surface extending away from the secondcushioning layer. The second cushioning layer is annular and borders acentral portion of the first cushioning layer above the domed lowersurface.

The multiple cushioning units may be arranged in different regions ofthe sole structure to provide a graded stiffness response. In someembodiments, the plurality of cushioning units includes interconnectedcushioning units having fluid communication between the second sealedchamber of each of the interconnected cushioning units. The fluidconnection may be accomplished by channels connecting the chambers, orby linking chambers, as discussed herein. For example, cushioning unitsin the heel region may be fluidly interconnected with other cushioningunits in the heel region and/or in one or more other regions, such asthe midfoot region and forefoot region. By fluidly interconnecting thecushioning units, a compressive force applied to one region of the solestructure affects pressure in the second sealed chambers of theinterconnected units. For example, a compressive force in the heelregion can displace some of the gas from the cushioning unit(s) in theheel region to cushioning units forward of the heel region via theinterconnected second sealed chambers. This effectively preloads thesecond chambers of cushioning units forward of the heel region toprovide a stiffer response upon compression of the second sealedchamber.

In some embodiments, the sole structure has a heel region, a forefootregion, and a midfoot region between the heel region and the forefootregion, and the interconnected cushioning units are disposed in the heelregion and the midfoot region and are arranged in a serpentine shape.For example, the serpentine shape may wind toward the lateral side, thentoward the medial side in progressing forward from the heel region,tracking the loading pattern of a typical foot strike and forward roll.

The interconnected cushioning units may be disposed in one or moreregions of the sole structure. For example, in one or more embodiments,the sole structure has a heel region, a forefoot region, and a midfootregion between the heel region and the forefoot region, and theinterconnected cushioning units are disposed in the forefoot region.

In some embodiments, the sole structure may include different groups ofthe interconnected cushioning units, each group isolated from the othergroup or groups. For example, the plurality of cushioning units mayinclude a first group of interconnected cushioning units in the forefootregion having fluid communication between the second sealed chamber ofeach of the interconnected cushioning units, and a second group ofinterconnected cushioning units disposed in the heel region and themidfoot region, the second group fluidly-isolated from the first groupand having fluid communication between the second sealed chamber of eachof the interconnected cushioning units of the second group. The firstgroup may thus be configured with a different stiffness profile than thesecond group, as may be beneficial for providing soft cushioning at heelstrike and a stiffer support at toe-off. In some embodiments, the secondgroup of interconnected cushioning units may be arranged in a serpentineshape. This allows the fluid in the interconnected second chambers ofthe second group to displace forward in correspondence with the forwardprogression of foot loading, providing a relatively stiffer secondchamber in forward ones of the interconnected cushioning units.

Some embodiments of midsole systems with interconnected cushioning unitsmay include one or more linking chambers. At least some of theinterconnected cushioning units laterally surround the linking chamber,with the second sealed chamber of each laterally-surroundinginterconnected cushioning unit in fluid communication with the linkingchamber.

In some embodiments, at least some of the multiple cushioning units arefluidly-isolated from one another in order to achieve a desiredcushioning response. For example, the plurality of cushioning units mayinclude multiple isolated cushioning units each disposed adjacent aperiphery of the sole structure, and each fluidly-isolated from allother ones of the plurality of cushioning units. Optionally,interconnected cushioning units may be disposed inward of the isolatedcushioning units relative to the periphery. Stated differently, themultiple isolated cushioning units may be disposed between the peripheryand the interconnected cushioning units. Such an arrangement enableseach peripheral cushioning unit to maintain a stiffness responseindependent of the progression of foot loading. For example, eachperipheral cushioning unit may be configured and pressurized to providea relatively stiff response, providing stability to discourageoverpronation and/or underpronation (supination).

In some embodiments in which the cushioning units have the domed lowersurface, the midsole system comprises a first polymeric sheet, a secondpolymeric sheet, and a third polymeric sheet. The first polymeric sheetand the second polymeric sheet define the first sealed chamber of eachof the plurality of cushioning units, and the first polymeric sheetdefines the domed lower surface of each of the plurality of cushioningunits. The second polymeric sheet and the third polymeric sheet definethe second sealed chamber of each of the plurality of cushioning units,and the second polymeric sheet and the third polymeric sheet are bondedto one another at bonds each of which extends over the central portionof the first sealed chamber of a respective one of the plurality ofcushioning units and is bordered by the second sealed chamber of therespective one of the plurality of cushioning units.

In one or more embodiments, the midsole system may further comprise athird cushioning layer overlying the plurality of cushioning units. Alower surface of the third cushioning layer has a plurality of recessesshaped such that the plurality of cushioning units are nested in thethird cushioning layer at the plurality of recesses. For example, thethird cushioning layer may be foam, with downward-facing recesses thatcup portions of the top surface of the cushioning units, nesting thecushioning units from above.

In one or more embodiments, the sole structure may further comprise anadditional cushioning layer underlying the plurality of cushioningunits. The additional cushioning layer may be another layer of themidsole system, or may be an outsole, or a combination of a midsolelayer and an outsole. The additional cushioning layer includes aplurality of stanchions, and each stanchion interfaces with the domedlower surface of a respective one of the plurality of cushioning units.For example, the stanchions may extend generally upward. At least someof the plurality of stanchions may have concave upper surfaces each ofwhich cups at least a portion of the domed lower surface of therespective one of the plurality of cushioning units. Accordingly, thestanchions are spaced apart from one another in correspondence withrelative spacing of the cushioning units such that the stanchions caninterface with the cushioning units in a one-to-one ratio. Undercompressive loading of a cushioning unit, the domed lower surface of thefirst cushioning layer is compressed against the stanchion.

The stanchions may be configured to affect the cushioning response ofthe sole structure as the foot moves forward from heel to toe. Forexample, in one or more embodiments, the plurality of stanchions maydecrease in height, increase in width, or both, from the heel region tothe forefoot region. Generally, a narrower stanchion relative to a domedlower surface of a cushioning unit will cause more of the firstcushioning layer to collapse over the stanchion, isolating loading tothe first cushioning layer for a greater range of displacement(compression) than a wider stanchion. A narrower stanchion relative tothe domed lower surface may provide a softer (less stiff) initialloading response. Similarly, a shorter stanchion allows lessdisplacement of the cushioning unit prior to the domed lower surface ofthe cushioning unit bottoming out relative to the stanchion, providing astiffer initial loading response relative to a taller stanchion.Additionally, the interface area of the stanchion (where it cups thedomed lower surface) to the total area of the domed lower surfacegoverns how the first cushioning layer can deform (compress). Generally,a larger ratio of the interface of the stanchion to the total area ofthe domed lower surface results in a stiffer response of the cushioningunit by minimizing the ability of the first cushioning layer to deformover the stanchion. In one or more embodiments, a ratio of stanchioninterface area to total area of the domed lower surface for each of theplurality of cushioning units may be greater on average for the forefootcushioning units interfacing with the forefoot stanchions than for theheel cushioning units interfacing with the heel stanchions. Accordingly,the less stiff first cushioning layer affects cushioning over a greaterrange of displacement in the heel region than in the forefoot region,providing a relatively stiffer response in the forefoot region, as isappropriate for supporting toe-off.

In one or more embodiments, a sole structure for an article of footwearcomprises a midsole system having a bladder comprising four stackedpolymeric sheets bonded to one another and defining a first cushioninglayer, a second cushioning layer, and a third cushioning layer, eachcushioning layer comprising a sealed chamber retaining gas in isolationfrom each other sealed chamber. The midsole system further comprises asole layer overlying the bladder and configured with a bottom surfacehaving an outer peripheral portion and a central portion surrounded bythe outer peripheral portion. The outer peripheral portion is mated withan upper surface of the bladder in an unloaded state of the solestructure, and the central portion is at least partially spaced apartfrom the upper surface of the bladder in the unloaded state of the solestructure. Stated differently, the outer peripheral portion is “keyed”to the corresponding outer peripheral portion of the bladder, while thecentral portion is not keyed to the bladder. This configuration allowsgreater displacement of the bladder relative to the central portion thanthe peripheral portion under compressive loading. A greater stiffnessprofile may thus be achieved at the peripheral portion, in order toprovide stability to counteract foot tendencies for overpronation andsupination. The central portion, in contrast, may achieve a softer (lessstiff) initial cushioning response, presenting a soft ride to themajority of the foot. The bladder will conform to the central portion ofthe bottom surface of the sole layer after the initial stage ofcompressive loading.

In addition to the bladder and the overlying sole layer with the keyedperipheral portion, the sole structure may further comprise anunderlying sole layer, such as an outsole or an additional midsolelayer, which underlies the bladder. An upper surface of the underlyingsole layer is mated with a bottom surface of the bladder in both theunloaded state and under compressive loading of the sole structure.

In one or more embodiments, a sole structure for an article of footwearcomprises a midsole system having a first cushioning unit and a secondcushioning unit, each cushioning unit including a first cushioning layercomprising a first sealed chamber, and a second cushioning layercomprising a second sealed chamber. The first sealed chamber and thesecond sealed chamber each retain gas in isolation from one another. Thefirst cushioning unit is inverted and the second cushioning unit isstacked on the first cushioning unit such that the first cushioninglayer of the first cushioning unit interfaces with and underlies thefirst cushioning layer of the second cushioning unit. In embodiments inwhich the first cushioning layer is less stiff than the secondcushioning layer, such as when the pressure of the gas in the firstcushioning layer is less than the pressure of the gas in the secondsealed chamber in an unloaded state, stacking the cushioning units sothat the least stiff first cushioning layers interface with one anothermay allow a greater range of displacement of the sole structure in aninitial (first) stage of compression that is affected only by the leaststiff first cushioning layers.

Such a stacked arrangement of cushioning units may be implemented withvarious configurations of cushioning units. For example, the cushioningunits may be those described above in which the first cushioning layerof each cushioning unit has a domed surface extending away from thesecond cushioning layer, and the second cushioning layer is annular andborders a central portion of the first cushioning layer. In such aconfiguration, the domed surface of the first cushioning unit interfaceswith the domed surface of the second cushioning unit.

In another alternative, the stacked arrangement of cushioning units maybe implemented in a configuration in which each cushioning unit has fourstacked polymeric sheets bonded to one another to define the firstsealed chamber bounded by the first polymeric sheet and the secondpolymeric sheet, the second sealed chamber bounded by the secondpolymeric sheet and the third polymeric sheet, and a third sealedchamber bounded by the third polymeric sheet and the fourth polymericsheet.

The above features and advantages and other features and advantages ofthe present teachings are readily apparent from the following detaileddescription of the modes for carrying out the present teachings whentaken in connection with the accompanying drawings.

Referring to the drawings wherein like reference numbers refer to likecomponents throughout the views, FIG. 1 shows an article of footwear 10.The article of footwear 10 includes a sole structure 12 and an upper 14secured to the sole structure 12. The upper 14 is configured to receiveand retain a foot 16 so that the foot 16 is supported on the solestructure 12 with the sole structure 12 positioned below the foot 16,and between the foot 16 and the ground, which is represented by a groundsurface G. As discussed herein, the sole structure 12 includes a midsolesystem 18 that has multiple cushioning units 19, each cushioning unithaving multiple cushioning layers disposed relative to one another suchthat the midsole system 18 absorbs a dynamic compressive load (such asdue to impact with the ground) in stages of progressive cushioning in asequence according to the relative stiffness of the cushioning layers.As used herein, “stiffness” of a cushioning layer is the ratio of changein compressive load (e.g., force in Newtons) to displacement of thecushioning layer (e.g., displacement in millimeters along the axis ofthe compressive load). An outsole 20 is secured to the midsole system 18as described herein. FIG. 9 is a bottom view of the midsole system 18,with the outsole 20 removed. FIG. 9 shows that the midsole system 18 haseight cushioning units 19A, 19B, 19C, 19D, 19E, 19F, 19G, 19H. Thecushioning units 19A-19H are referred to with reference numeral 19 whendiscussing features common to each of the cushioning units 19A-19H. Inthe embodiment of FIG. 9, each of the cushioning units 19A-19H is influid communication with each of the other cushioning units via channels43 that interconnect the respective second cushioning layer 24 ofadjacent ones of the cushioning units. As further discussed herein, thefluid interconnection allows gas within the second sealed chambers 40 ofthe fluidly-interconnected cushioning units 19 in the heel region to bedisplaced to the cushioning units in the midfoot region and, ifinterconnected, to the forefoot region following, for example, a heelstrike, increasing stiffness of the midfoot and forefoot cushioningunits as the foot rolls forward to toe-off. In other embodiments shownand discussed herein, some or all of the cushioning units 19 may insteadbe fluidly-isolated from some or all of the other cushioning units.

With reference to FIGS. 2 and 4, a single one of the cushioning units 19of the midsole system 18 is shown. The cushioning unit 19 includes afirst cushioning layer 22, a second cushioning layer 24, and a thirdcushioning layer 26. As is evident in FIGS. 1 and 9, the thirdcushioning layer 26 extends in a forefoot region 13, a midfoot region15, and a heel region 17 of the midsole system 18. The midfoot region 15is between the heel region 17 and the forefoot region 13. As isunderstood by those skilled in the art, the forefoot region 13 generallyunderlies the toes and metatarsal-phalangeal joints of an overlying foot16. The midfoot region 15 generally underlies the arch region of thefoot 16. The heel region 17 generally underlies the calcaneus bone. Thefirst cushioning layer 22, the second cushioning layer 24, and the thirdcushioning layer 26 are stacked with the second cushioning layer 24partially overlying the first cushioning layer 22, and the thirdcushioning layer 26 overlying the second cushioning layer 24 when thearticle of footwear 10 is worn on a foot 16 so that the sole structure12 is disposed with the third cushioning layer 26 nearest the foot 16and the first cushioning layer 22 nearest the ground surface G, such aswhen the outsole 20 is in contact with the ground surface G. The firstcushioning layer 22 includes a ground-facing outer surface 28 of themidsole system 18, and the third cushioning layer 26 includes afoot-facing outer surface 30 of the midsole system 18. The ground-facingouter surface 28 is a domed lower surface of the cushioning unit 19. Asis apparent in FIG. 2, the first cushioning layer 22 underlies thesecond cushioning layer 24, and the domed lower surface 28 extends awayfrom the second cushioning layer 24. The second cushioning layer 24 isannular and borders a central portion of the first cushioning layer 22(i.e., the portion between the phantom lines 56 of FIG. 4, as discussedherein.

The midsole system 18 includes a first polymeric sheet 32, a secondpolymeric sheet 34, and a third polymeric sheet 36. The first cushioninglayer 22 is formed by the first and second polymeric sheets 32, 34,which form and define a first sealed chamber 38 bounded by the firstpolymeric sheet 32 and the second polymeric sheet 34. The secondcushioning layer 24 is formed by the second polymeric sheet 34 and thethird polymeric sheet 36, which form and define a second sealed chamber40 bounded by the second polymeric sheet 34 and the third polymericsheet 36.

The first, second, and third polymeric sheets 32, 34, 36 are a materialthat is impervious to gas, such as air, nitrogen, or another gas. Thisenables the first sealed chamber 38 to retain a gas at a firstpredetermined pressure, and the second sealed chamber 40 to retain a gasat a second predetermined pressure. A third cushioning layer 26 of themidsole system 18 is removed in FIG. 2. FIG. 4 shows the same portion ofthe sole structure 12 as FIG. 2, but with the third cushioning layer 26included. Having the first sealed chamber 38 of the cushioning unit 19shown not in fluid communication with the first sealed chamber 38 of anyof the other cushioning units 19 or with the second sealed chamber 40 orchambers of the same or other cushioning units 19 allows separate,discrete, first sealed chambers 38 to be optimized in geometry andpressure for various areas of the foot. For example, the cushioningunits 19 can be customized in number, size, location, and fluid pressurefor a foot map of pressure loads of a specific wearer, or for apopulation average of wearers of the particular size of footwear.Separate cushioning units 19 also enhance flexibility of the midsolesystem 18 as areas between the cushioning units 19 are of reducedthickness, as is apparent in the side view of FIG. 2, and thus reducebending stiffness of the midsole system 18. For example, areas ofwebbing (also referred to herein as bonds), best shown in FIG. 9, wherethe first and second polymeric sheets 32, 34 are bonded to one anotherbetween the domed first chambers 38 of adjacent cushioning units 19, areof reduced thickness. The areas between cushioning units 19 function asflex grooves and can be disposed at desired flex regions of the midsolesystem 18. In FIG. 9, channels 43 are shown that connect the secondchambers 40 of each cushioning units 19 for fluid communication with oneanother.

The polymeric sheets 32, 34, 36 can be formed from a variety ofmaterials including various polymers that can resiliently retain a fluidsuch as air or another gas. Examples of polymer materials for polymericsheets 32, 34, 36 include thermoplastic urethane, polyurethane,polyester, polyester polyurethane, and polyether polyurethane. Moreover,the polymeric sheets 32, 34, 36 can each be formed of layers ofdifferent materials. In one embodiment, each polymeric sheet 32, 34, 36is formed from thin films having one or more thermoplastic polyurethanelayers with one or more barrier layers of a copolymer of ethylene andvinyl alcohol (EVOH) that is impermeable to the pressurized fluidcontained therein as disclosed in U.S. Pat. No. 6,082,025, which isincorporated by reference in its entirety. Each polymeric sheet 32, 34,36 may also be formed from a material that includes alternating layersof thermoplastic polyurethane and ethylene-vinyl alcohol copolymer, asdisclosed in U.S. Pat. Nos. 5,713,141 and 5,952,065 to Mitchell et al.which are incorporated by reference in their entireties. Alternatively,the layers may include ethylene-vinyl alcohol copolymer, thermoplasticpolyurethane, and a regrind material of the ethylene-vinyl alcoholcopolymer and thermoplastic polyurethane. The polymeric sheets 32, 34,36 may also each be a flexible microlayer membrane that includesalternating layers of a gas barrier material and an elastomericmaterial, as disclosed in U.S. Pat. Nos. 6,082,025 and 6,127,026 to Bonket al. which are incorporated by reference in their entireties.Additional suitable materials for the polymeric sheets 32, 34, 36 aredisclosed in U.S. Pat. Nos. 4,183,156 and 4,219,945 to Rudy which areincorporated by reference in their entireties. Further suitablematerials for the polymeric sheets 32, 34, 36 include thermoplasticfilms containing a crystalline material, as disclosed in U.S. Pat. Nos.4,936,029 and 5,042,176 to Rudy, and polyurethane including a polyesterpolyol, as disclosed in U.S. Pat. Nos. 6,013,340, 6,203,868, and6,321,465 to Bonk et al. which are incorporated by reference in theirentireties. In selecting materials for the polymeric sheets 32, 34, 36,engineering properties such as tensile strength, stretch properties,fatigue characteristics, dynamic modulus, and loss tangent can beconsidered. The thicknesses of polymeric sheets 32, 34, 36 can beselected to provide these characteristics.

The first and second sealed chambers 38, 40 are not in fluidcommunication with one another. Stated differently, the first and secondsealed chambers 38, 40 are sealed from one another by the secondpolymeric sheet 34. This allows the first and second sealed chambers 38,40 to retain gas at different pressures. The first sealed chamber 38retains gas at a first predetermined pressure when the midsole system 18in an unloaded state, and the second sealed chamber 40 retains gas at asecond predetermined pressure in the unloaded state. The unloaded stateis the state of the midsole system 18 when it is not under either steadystate or dynamic loading. For example, the unloaded state is the stateof the midsole system 18 when it is not bearing any loads, such as whenit is not on the foot 16. The second predetermined pressure can bedifferent than the first predetermined pressure. In the embodimentshown, the second predetermined pressure is higher than the firstpredetermined pressure. In one non-limiting example, the firstpredetermined pressure is 7 pounds per square inch (psi), and the secondpredetermined pressure is 20 psi. The predetermined pressures may beinflation pressures of the gas to which the respective sealed chambers38, 40 are inflated just prior to finally sealing the chambers 38, 40.The lowest one of the predetermined pressures, such as the firstpredetermined pressure, may be ambient pressure rather than an inflatedpressure. The different cushioning units 19 can have different pressuresin their respective first sealed chambers 38, as the first sealedchambers 38 are not in fluid communication with one another. Forexample, pressures of the first sealed chambers 38 of cushioning units19 in the heel region 17 can be lower than pressures in the midfootregion 15 and/or the forefoot region 13.

In the embodiment shown, the third cushioning layer 26 is foam. By wayof non-limiting example, the foam of the third cushioning layer 26 maybe at least partially a polyurethane foam, a polyurethane ethylene-vinylacetate (EVA) foam, and may include heat-expanded and molded EVA foampellets.

The first cushioning layer 22 has a first stiffness K1 that isdetermined by the properties of the first and second polymeric sheets32, 34, such as their thicknesses and material, and by the firstpredetermined pressure in the first sealed chamber 38. The secondcushioning layer 24 has a second stiffness K2 that is determined by theproperties of the second and third polymeric sheets 34, 36, such astheir thicknesses and material, and by the second predetermined pressurein the second sealed chamber 40. The third cushioning layer 26 has athird stiffness K3 that is dependent on the properties of the foammaterial, such as the foam density. The stiffness K1, K2, and/or K3 neednot be linear throughout a stage of compression. For example, thestiffness K3 of the third cushioning layer may increase exponentiallywith displacement.

A dynamic compressive load on the sole structure 12 is due to an impactof the article of footwear 10 with the ground, as indicated by a footbedload FL of a person wearing the article of footwear 10 and an oppositeground load GL. The footbed load FL is shown in FIGS. 5-7 as a series ofarrows acting on the foot-facing outer surface 30, and the ground loadGL is shown as a series of arrows acting on a ground contact surface 35of the outsole 20. The footbed load FL is represented by all of thedownward arrows on the foot-facing outer surface 30. The ground load GLis represented by all of the upward arrows on the ground contact surface35. The dynamic compressive load is absorbed by the first cushioninglayer 22, the second cushioning layer 24, and the third cushioning layer26 of a particular cushioning unit 19 in a sequence according toincreasing magnitudes of the first stiffness K1, the second stiffnessK2, and the third stiffness K3 from least stiff to most stiff. In theembodiment shown, the stiffness of the cushioning layers 22, 24, 26increase in the following order: first stiffness K1, third stiffness K3,and second stiffness K2, and the dynamic compressive load is thusabsorbed by the cushioning layers in the following order: firstcushioning layer, 22, third cushioning layer 26, and second cushioninglayer 24 but any combination of relative pressures is possible.

The second polymeric sheet 34 and the third polymeric sheet 36 arebonded to one another between the first sealed chamber 38 and the thirdcushioning layer 26 at a bond 42 (also referred to herein as webbing)having an outer periphery 44 with a closed shape. In the embodimentshown, the closed shape is substantially circular, as best shown in thebottom view of FIG. 9, where the bond 42 is visible through the firstpolymeric sheet 32. The polymeric sheets are indicated as substantiallytransparent. Alternatively, any or all of the polymeric sheets couldinstead be opaque. The second sealed chamber 40 borders the outerperiphery 44 of the bond 42. All three of the first polymeric sheet 32,the second polymeric sheet 34, and the third polymeric sheet 36 arebonded to one another at a peripheral flange 46 at an outer periphery ofthe midsole system 18 as shown in FIG. 4. The bond 42 is disposedsubstantially level with an uppermost extent 49 of the second sealedchamber 40 when the sole structure 12 is unloaded, as indicated in FIGS.2 and 4. At the time of bonding the second and third polymeric sheets34, 36 at the bond 42, all of the polymeric sheets 32, 34, 36, are inthe initial, flat stacked state. The bond 42 can be positioned at theuppermost extent 49 of the second sealed chamber 40 by inflating thesecond sealed chamber 40 prior to inflation of the first sealed chamber38, and at a higher inflation pressure than the first sealed chamber 38.When inflation occurs in this order with these relative inflationpressures, the bond 42 will roll upward from a position substantiallylevel with the flange 46 to the position shown in FIGS. 2 and 4 as thefirst sealed chamber 38 is inflated and sealed. The third cushioninglayer 26 is thereafter bonded to the upper surface 54 of the thirdpolymeric sheet 36.

With the bond 42 disposed substantially level with an uppermost extent49 of the second sealed chamber 40, a relatively flat upper surface 54is presented to the third cushioning layer 26 at the uppermost extent 49of the second cushioning layer 24. This helps to enable a relativelyflat foot-facing outer surface 30 of the midsole system 18 if such isdesired. For example, the cushioning unit 19 illustrated in FIGS. 2 and4 extends generally the width of the footbed at a heel portion 17 of thesole structure 12, as is evident in FIG. 9. Because the bond 42 ishigher than the flange 46, there is no depression or central cavitybetween the uppermost extent 49 and a top surface of the bond 42. Inother embodiments, the bond 42 need not be level with the uppermostextent 49, in which case a cavity between the bond and the uppermostextent 49 can be left as a void at ambient pressure under the thirdcushioning layer 26, or can be filled by the third cushioning layer 26.

Although the bond 42 is shown as substantially circular, in otherembodiments, the closed shape may be substantially oval, or may be anequilateral polygon, such as a substantially triangular bond or asubstantially rectangular. It should be appreciated that each of theclosed shapes may have rounded corners. Equilateral closed shapes arerelatively easy to dispose closely adjacent to one another in variousorientations to cover select portions of a midsole. Each bond issurrounded at an outer periphery by an annular second cushioning layerhaving substantially the same shape as the bond which it surrounds. Abond that has any of these closed shapes also enables the firstpolymeric sheet 32 to have a ground-facing outer surface 28 that is adomed lower surface such as shown in FIG. 4. The unrestrained portion ofthe first sealed chamber 38 tends to adopt the domed shape due to theforce of the internal gas pressure on the inner surfaces of thepolymeric sheets 32, 34 bounding the first sealed chamber 38.

Selection of the shape, size, and location of various bond portions of amidsole, such as the midsole system 18, enables a desired contouredouter surface of the finished midsole system. Prior to bonding at thebond 42, at the flange 46, and at the bond 47 discussed below, thepolymeric sheets 32, 34, 36 are stacked, flat sheets. Anti-weld materialmay be ink-jet printed at all selected locations on the sheets wherebonds are not desired. For example, the anti-weld material may beprinted on both sides of the second polymeric sheet 34 and/or on theupper surface of the first polymeric sheet 32, and the upper surface ofthe second polymeric sheet 34. The stacked, flat polymeric sheets arethen heat pressed to create bonds between adjacent sheets on alladjacent sheet surfaces except for where anti-weld material was applied.No radio frequency welding is necessary.

Once bonded, the polymeric sheets 32, 34, 36 remain flat, and take onthe contoured shape only when the chambers 38, 40 are inflated and thensealed. The polymeric sheets 32, 34, 36 are not thermoformed.Accordingly, if the inflation gas is removed, and assuming othercomponents are not disposed in any of the sealed chambers, and thepolymeric sheets are not yet bonded to other components such as theoutsole 20 or the cushioning layer 26, the polymeric sheets 32, 34, 36will return to their initial, flat state. The outsole 20 is bonded tothe ground-facing outer surface 28 by adhesive or otherwise only afterinflation and sealing of the first sealed chamber 38.

In the embodiment shown in FIG. 2, the second sealed chamber 40 is anannulus (i.e., is substantially annular) that has the equilateral shapeof the bond 42 that it borders. In the embodiment of FIG. 2, the secondchamber 40 is a ring-shaped annulus (i.e., generally toroidal). A bondthat has one of the closed shapes discussed herein enables theground-facing outer surface 28 of the underlying first polymeric sheet32 to adopt a domed shape that is substantially centered under the bond,as shown by the domed ground-facing outer surface 28 (also referred toas a domed lower surface 28 or domed portion 28) centered under bond 42and extending away from the second and third cushioning layers 24, 26.The domed lower surface 28 is thus also centered under and stabilized bythe higher pressure second sealed chamber 40 of the second cushioninglayer 24, which borders and surrounds the outer periphery 44 of the bond42. A domed ground-facing outer surface provides a relatively largeamount of vertical displacement of the first cushioning layer 22 underdynamic compression in comparison to a flat lower surface, prolongingthe stage of load absorption by the first cushioning layer 22. The firststage of compression is represented by portion 102 of the load versusdisplacement curve 100 of FIG. 8 that represents the absorption of thedynamic compressive load by the first cushioning layer 22 with the firststiffness K1, which, in the embodiment of FIGS. 2 and 4-7 is the leaststiff cushioning layer.

With reference to FIG. 4, a central portion of the first sealed chamber38 directly underlies the third cushioning layer 26 as a bond 42 and aperipheral portion of the first sealed chamber 38 directly underlies aportion of the second sealed chamber 40. The central portion is betweenlines 56 and the peripheral portion is outward of lines 56. The firstpolymeric sheet 32 and the second polymeric sheet 34 are bonded to oneanother at a bond 47 along an outer peripheral portion 48 of anunderside 50 of the second sealed chamber 40. Accordingly, the firstsealed chamber 38 underlies the second sealed chamber 40 only inward ofthe outer peripheral portion 48 (i.e., only inward of the phantom lines52). The portion of the second sealed chamber 40 overlying the firstsealed chamber 38 is the annular portion between the phantom lines 52and 56. The bond 47 reduces the height of the first sealed chamber 38under the bond 42 to height H1, which is lower in comparison to a heightthat would exist if the first and second polymeric sheets 32, 34 werebonded to one another only at the flange 46. A reduced height of thefirst sealed chamber 38 may enhance the stability of the firstcushioning layer 22 in that it may minimize tilting or tipping of thedomed ground-facing outer surface 28 during compression. By varying thesize of the bond 47, the height H1 and thus the amount of displacementavailable in compression of the first cushioning layer 22 can be tuned,affecting the domain of the low rate portion 102 of the load versusdisplacement curve 100 (i.e., the displacement over which the low rateportion 102 extends).

As discussed, the second sealed chamber 40 directly overlies only theperipheral portion of the first sealed chamber 38. The peripheralportion is the ring-shaped portion between the phantom lines 52 and 56.The third cushioning component 26 directly overlies only a remainingcentral portion of the first sealed chamber 38, i.e., that portionbetween (inward of) the phantom lines 56. With this relative dispositionof the cushioning layers 22, 24, 26, the first cushioning layer 22absorbs the dynamic compressive load in series with the secondcushioning layer 24 and the third cushioning layer 26 at the peripheralportion of the first sealed chamber 38 (the portion between phantomlines 52 and 56), and the first cushioning layer 22 absorbs the dynamiccompressive load in parallel with the second cushioning layer 24 and inseries with the third cushioning layer 26 at the central portion of thefirst sealed chamber 38 (the portion between the phantom lines 56). Asused herein, a cushioning layer directly overlies another cushioninglayer when it is not separated from the cushioning layer by a cushioningportion of an intervening cushioning layer (i.e., a foam portion or agas-filled sealed chamber). A bond that separates cushioning layers,such as bond 42, is not considered a cushioning portion of a cushioninglayer. Accordingly, cushioning layers are considered to directly overlieone another when separated only by a bond. The first sealed chamber 38directly underlies the bond 42 and the third cushioning layer 26directly overlies the bond 42. The third cushioning layer 26 directlyoverlies the remaining portion of the first sealed chamber 38 as it isseparated from the remaining portion of the first sealed chamber 38 onlyby bond 42 and not by the second sealed chamber 40.

As described, the second cushioning layer 24 is disposed at leastpartially in series with the first cushioning layer 22 relative to adynamic compressive load FL, GL applied on the midsole system 18. Morespecifically, the first cushioning layer 22 and the second cushioninglayer 24 are in series relative to the load FL, GL between the phantomlines 52 and 56. The third cushioning layer 26 is disposed at leastpartially in series with the first cushioning layer 22 and at leastpartially in series with the second cushioning layer 24 relative to thedynamic compressive load FL, GL. More specifically, the third cushioninglayer 26 is directly in series with the first cushioning layer 22 inwardof the phantom lines 56. The first cushioning layer 22, the secondcushioning layer 24, and the third cushioning layer 26 are in seriesrelative to the dynamic compressive load FL, GL between the phantomlines 52 and 56. The third cushioning layer 26 is in series with thefirst cushioning layer 22 but not the second cushioning layer 24 betweenthe phantom lines 56. The third cushioning layer 26 is in series withthe second cushioning layer 24 but not the first cushioning layer 22outward of the phantom lines 52.

The outsole 20 is secured to the domed lower surface 28 of the firstpolymeric sheet 32. The outsole 20 includes a central lug 60substantially centered under the domed lower surface 28 of the firstpolymeric sheet 32 and serving as ground contact surface 35. The outsole20 also includes one or more side lugs 62 disposed adjacent the centrallug 60, i.e., surrounding the central lug 60 and further up the sides ofthe domed ground-facing outer surface 28. The side lugs 62 are shorterthan the central lug 60, and are configured such that they are not incontact with (i.e., are displaced from) the ground surface G when thesole structure 12 is unloaded, or is under only a steady state load or adynamic compressive load not sufficiently large to cause compression ofthe first sealed chamber 38 to the state of FIG. 5. The lugs 60, 62 maybe an integral portion of the outsole 20 as shown in FIGS. 2 and 4. Inan alternative embodiment of a sole structure 12A shown in FIG. 3, anoutsole 20A has a central lug 60A and side lugs 62A not integrallyformed with but secured to the outsole 20A so that the outsole 20A withthe lugs 60A, 62A functions as a unitary component and in a mannersubstantially the same as outsole 20 and lugs 60, 62.

The width W1 of the central lug 60 at the ground contact surface G isless than a width W2 of the domed lower surface 28 of the firstpolymeric sheet 32. Because the central lug 60 rests on the groundsurface G, the reaction load (ground load GL) of the dynamic compressiveload on the midsole system 18 is initially applied through the centrallug 60 toward a center of the domed lower surface 28 of the firstpolymeric sheet 32 where the maximum available displacement of the firstsealed chamber 38 exists (i.e., at the greatest height H1 of the firstsealed chamber 38). Because the central lug 60 is not as wide as thefirst sealed chamber 38, the first sealed chamber 38 may compress aroundthe central lug 60.

The material of the outsole 20 in the embodiment shown has a fourthstiffness K4 (i.e., compressive stiffness) that is greater than thefirst stiffness K1 of the first cushioning layer 22, and may be more orless stiff than either or both of the second stiffness K2 of the secondcushioning layer 24 and the third stiffness K3 of the third cushioninglayer 26. For example, the outsole 20 could be polymeric foam, such asinjected foam. In the embodiment shown, the fourth stiffness K4 isgreater than the first stiffness K1, the second stiffness K2, and thethird stiffness K3.

With reference to FIGS. 5-8, the stages of absorption of the dynamiccompressive load FL, GL, represented by the footbed load FL and theground load GL, are schematically depicted assuming that the firststiffness K1 of the first cushioning layer 22 is less than the secondstiffness K2 of the second cushioning layer 24, and the third stiffnessK3 of the third cushioning layer 26 is greater than the first stiffnessK1 and less than the second stiffness K2. When the sole structure 12initially receives the dynamic compressive load FL, GL, a first stage ofcompression I occurs, in which the least stiff first cushioning layer 22is the first to compress, and compresses around the lug 60, changing theshape of the first sealed chamber 38 and compressing the gas in thefirst sealed chamber 38 such that the overall volume of the first sealedchamber 38 reduces relative to the state shown in FIGS. 2 and 4. Thefirst stage of compression I is represented in FIG. 5. Compression ofthe second sealed chamber 40, the third cushioning layer 26, and theoutsole 20 in the first stage of compression I, either does not occur oris only minimal. In the first stage of compression I shown in FIG. 5,the compression of the first sealed chamber 38 moves the side lugs 62level with the central lug 60, causing the side lugs 62 to now form partof the ground contact surface 35 over which the ground load GL isspread, such that the ground contact surface 35 is larger in areacompared to the steady-state loading of FIGS. 2 and 4. The midsolesystem 18 has an effectively linear stiffness during the first stage ofcompression I, as represented by the portion 102 of the stiffness curve100, with a numerical value substantially equal to the first stiffnessK1.

In the second stage of compression II, shown in FIG. 6, the thirdcushioning layer 26 begins compressing, as indicated by the decreasedthickness of the third cushioning layer 26 in comparison to FIG. 5.Compression of the first sealed chamber 38 of the first cushioning layer22 may continue in series with compression of the third cushioning layer26 in the second stage of compression II, assuming that the firstcushioning layer 22 has not reached its maximum compression under thedynamic compressive load. The midsole system 18 has an effectivestiffness during the second stage of compression II that is a dependentupon the third stiffness K3, and may be partially dependent on the firststiffness K1. The effective stiffness of the midsole system 18 duringthe second stage of compression II is represented by the portion 104 ofthe stiffness curve 100 in FIG. 8.

In the third stage of compression III, shown in FIG. 7, the secondcushioning layer 24 begins compressing by compression of the gas in thesecond sealed chamber 40. If compression of the first sealed chamber 38has not yet reached its maximum compression under the dynamiccompressive load, then compression of the first sealed chamber 38 willcontinue in series with the second cushioning layer 24, such as in thevolume between phantom lines 52 and 56, and in parallel with the secondcushioning layer 24 in the volume between lines 56. If compression ofthe third cushioning layer 26 has not already reached its maximum underthe dynamic compressive load in the second stage II, then compression ofthe third cushioning layer 26 will continue during the third stage IIIin series with compression of the second cushioning layer 24 and inseries with compression of the first cushioning layer 22, assumingcompression of the first cushioning layer 22 has not already reached itsmaximum under the dynamic compressive load. The stiffness K4 of theoutsole 20 can be selected such that compression of the outsole 20 willnot begin until after the third stage of compression III.

The midsole system 18 has an effective stiffness in the third stage ofcompression III that corresponds mainly with the relatively stiff secondcushioning layer 24. Sealed chambers of compressible gas tend to quicklyramp in compression in a non-linear manner after an initial compression.The effective stiffness of the midsole system 18 during the third stageof compression III is dependent upon the second stiffness K2,potentially to a lesser extent in part on the first stiffness K1 (if thefirst sealed chamber 38 continues compressing in series and/or parallelwith the second sealed chamber 40), and potentially to a lesser extentin part on the third stiffness K3 (if the foam of the cushioning layer26 continues compressing in series and/or parallel with the secondsealed chamber 40). The effective stiffness of the midsole system 18during the third stage of compression III is represented by the portion106 of the stiffness curve 100 in FIG. 8. Because the third stage ofcompression III occurs after the first and second stages, it maycoincide with movement of the article of footwear 10 to a dorsiflexedposition in which an athlete is nearing a final toe-off position (i.e.,when completing a forward step or stride just prior to the article offootwear being lifted out of contact with the ground). Greatercompressive stiffness may be desirable at toe off to provide the athletewith a sensation of connection to the ground, in comparison to at theinitial impact when energy absorption and isolation from the ground ismost desirable.

Additionally, because in the embodiment shown, the second sealedchambers 40 of each of the cushioning units 19A-19H are in fluidcommunication with one another, compression of the second sealed chamber40 of the rearmost cushioning unit 19A in the heel region 17 candisplace gas forward to the second sealed chamber 40 of the adjacentcushioning unit 19B, then to cushioning unit 19C, and so on forward tocushioning unit 19H. The advancement of the displaced gas is encouragedby the natural rolling of the foot 16 forward from heel to toe.Accordingly, by the time of toe-off, the pressures in the second sealedchambers 40 of the forward-most cushioning units, such as 19G, 19E, and19H, are greater than the initial pressure of the second sealed chamber40 of the rearmost cushioning unit 19A, supporting the foot duringtoe-off, and effectively returning energy from the heel strike at theforefoot.

As best shown in FIGS. 1 and 4, the third cushioning layer 26 overlaysall of the various cushioning units. The cushioning layer 26 acts as acarrier that effectively holds the cushioning units relative to oneanother. More specifically, the cushioning layer 26 has a lower surface25 that has a plurality of recesses 27 shaped such that the cushioningunits 19A-19H are nested in the third cushioning layer 26, each at arespective recess 27. The cushioning units 19A-19H are only partiallynested in the cushioning layer 26, with the portion above the flange 46in the respective recess 27. The cushioning units 19A-19H can be securedto the cushioning layer 26 in the recesses 27 such as with adhesive orby thermal bonding. The third cushioning layer 26 may also have smallchannel recesses interconnecting the recesses 27 and receiving thechannels 43 of FIG. 9, or the channels 43 may be un-nested, just belowthe lower surface 25 of the third cushioning layer 26.

FIG. 10 shows another embodiment of a third cushioning layer 26A for usewith a midsole system 18 including multiple cushioning units 19. Thethird cushioning layer 26A includes a plurality of recesses 27A, 27B ata lower surface 25 for receiving and partially nesting the cushioningunits 19. The recess 27A are peripheral recesses, located adjacent aperiphery 29 of the third cushioning layer 26A, which is also theperiphery of the sole structure 12. The periphery 29 has a medialperiphery 29A, and a lateral periphery 29B. The recesses 27B are centralrecesses, disposed inward relative to the peripheral recesses 27A sothat the peripheral recesses 27A are between the periphery 29 and thecentral recesses 27B. In an embodiment, cushioning units 19 disposed inthe peripheral recesses 27A are each fluidly isolated from each otherone of the cushioning units 19. In contrast the cushioning units 19disposed in the central recesses 27B may be in fluid communication withone another via channels 43, and are referred to as interconnectedcushioning units. Such an arrangement enables each peripheral cushioningunit (i.e., the isolated cushioning units 19 disposed at the peripheralrecesses 27A) to maintain a stiffness response independent of theprogression of foot loading. For example, each peripheral cushioningunit may be configured and pressurized to provide a relatively stiffresponse, providing stability to discourage overpronation and/orunderpronation (supination). The interconnected, central cushioningunits 19 disposed at the central recesses 27B would allow gas to bedisplaced amongst the second sealed chambers 40 of the respectivecentral cushioning units, which may provide energy return by utilizingthe pressure at more rearward units, which may be subjected to loadingprior to the more forward central units, to add stiffness to the moreforward units via the added pressure of the transferred gas.

FIGS. 11-12 show one example of a midsole system 18A with a group ofinterconnected cushioning units 19, referred to with reference numbers19A1, 19B1, and 19C1. Each of the cushioning units is identical tocushioning unit 19 shown and described with respect to FIG. 2. Thesecond sealed chambers 40 of the respective cushioning units are fluidlyconnected with one another by fluid channels 43 formed by and betweenthe second and third polymeric sheets 34, 36. In the embodiments shown,dual channels 43 are shown between the cushioning units 19A1, 19B1,19C1. As is evident in FIG. 12, the domed lower surfaces 28 of therespective cushioning units 19A1, 19B1, 19C1 protrude and extend awayfrom the second sealed chambers 40. Additional channels 43A, 43B incommunication with the second sealed chamber 40 of the cushioning unit19A1 are shown with a seal 51, closing off the interconnected cushioningunits 19A1, 19B1, 19C1, so that no other cushioning units cancommunicate with those of the interconnected cushioning units 19A1,19B1, 19C1.

FIGS. 13-16 show another embodiment of a midsole system 118 for a solestructure of an article of footwear. The midsole system 118 comprises aplurality of cushioning units 19 as described with respect to FIGS. 2-8.The cushioning units 19 are all interconnected cushioning units as theyare effectively interconnected with one another via the channels 43shown between various adjacent cushioning units 19. Only some of thecushioning units 19 and channels 43 are labelled for clarity in thedrawings.

The midsole system 118 also comprises two sets of linking chambers 51A,51B. The linking chambers 51A link (i.e., fluidly-connect) the secondsealed chambers 40 of at least some of the laterally-surroundingcushioning units 19. Stated differently, for each linking chamber 51A,at least some of the interconnected cushioning units 19 laterallysurround the linking chamber 51A. The respective second sealed chamber40 of each of these laterally-surrounding interconnected cushioningunits 19 is in fluid communication with the linking chamber 51A via arespective channel 43. The linking chambers 51A do not have the bond 42between the second polymeric sheet 34 and the third polymeric sheet 36,so they create upward-extending domes 53 at the upper surface 54 of thethird polymeric sheet 36, as best seen in the perspective view of FIG.15. The domes 53 extend above the remainder of the upper surface 54.

The linking chambers 51B link (i.e., fluidly-connect) the first sealedchambers 38 of at least some of the laterally-surrounding cushioningunits 19. Stated differently, for each linking chamber 51B, at leastsome of the interconnected cushioning units 19 laterally surround thelinking chamber 51B. The respective first sealed chamber 38 of each ofthese laterally-surrounding, interconnected cushioning units 19 is influid communication with the linking chamber 51B via a respectivechannel 43B. The linking chambers 51B create downward-extending domes 55at the lower surface 57 of the first polymeric sheet 32, as best seen inthe FIG. 16. The domes 55 extend generally in a similar manner as thedomed lower surfaces 28 of the linked, laterally surrounding cushioningunits 19.

The linking chambers 51A permit the second chambers 40 of the laterallysurrounding cushioning units 19 to more quickly and evenly distributeand react to a compressive load on any one or more of the linked,laterally surrounding chambers 40. Similarly, the linking chambers 51Bpermit the first chambers 38 of the laterally surrounding cushioningunits 19 to more quickly and evenly distribute and react to acompressive load on any one or more of the linked, laterally surroundingchambers 38.

FIG. 17 shows another embodiment of a sole structure 212 for an articleof footwear. The sole structure 212 includes a midsole system 218 thatcomprises a plurality of cushioning units 19 as described with respectto FIGS. 2-8. The plurality of cushioning units 19 include both fluidlyisolated cushioning units 19P, and different groups of interconnectedcushioning units 19Q and 19R. The cushioning units 19P, 19Q, and 19R arereferred to with reference numeral 19 when discussing features common toeach of the cushioning units 19A-19H. Each of the cushioning units 19 ispartially nested in a respective recess of an overlaying thirdcushioning layer 26B, as discussed with respect to cushioning layers 26and 26A. More specifically, the plurality of cushioning units includemultiple isolated cushioning units 19P each disposed adjacent aperiphery 29 of the sole structure 212, and each fluidly-isolated fromall other ones of the plurality of cushioning units 19. A first group ofinterconnected cushioning units 19R and a second group of interconnectedcushioning units 19Q are disposed inward of the isolated cushioningunits 19P relative to the periphery 29. Stated differently, the multipleisolated cushioning units 19P are disposed between the periphery 29 andthe interconnected sets of cushioning units 19Q, 19R. By isolating eachperipheral cushioning unit 19P, each peripheral cushioning unit 19P canmaintain a stiffness response independent of the progression of footloading. For example, each peripheral cushioning unit 19P may beconfigured and pressurized to provide a relatively stiff response,providing stability to discourage overpronation and/or underpronation(supination).

The first group of interconnected cushioning units 19R is in theforefoot region 13, and each are interconnected via channels 43 andlinking chambers 51A, 51B as described with respect to FIG. 16, so thatall of the first chambers 38 are fluidly connected, and all of thesecond chambers 40 are fluidly connected. The first group ofinterconnected cushioning units 19R extend only in the forefoot region13, and can be tuned with inflation pressures in the linked firstchambers 38, and the linked second chambers 40 suitable for toe-off.

The second group of interconnected cushioning units 19Q is disposed inthe heel region 17 and the midfoot region 15 and each isfluidly-isolated from the first group 19R and from the peripheralcushioning units 19P. The cushioning units 19Q are interconnected viachannels 43 and linking chambers 51A, 51B as described with respect toFIG. 16, so that all of the first chambers 38 are fluidly connected, andall of the second chambers 40 are fluidly connected. The interconnectedcushioning units 19Q of the second group are arranged in a serpentineshape. The serpentine shape may also be referred to as an “S” shape. Theserpentine shape winds from the rearmost unit 19Q1 forward toward thelateral side at unit 19Q2, then forward toward the medial side at unit19Q3, then finally back toward the center at unit 19Q4 in progressingforward from the heel region, tracking the loading pattern of a typicalfoot strike and forward roll. The loading pattern of the foot roll canpush some of the gas in the respective sealed chambers 38, 40 of thesecond group of cushioning units 19Q from the heel toward the midfoot,allowing the pressure at the heel 17 at impact to be lower than theloaded pressure of the midfoot 15 in the same interconnected chambers38, 40.

FIGS. 18-20 show another embodiment of a sole structure 312 thatincludes a midsole system 318 comprising a plurality of cushioning units19 each described as described with respect to FIGS. 2-8. As shown inFIG. 18, each cushioning unit 19 is partially nested in a recess 27 inthe bottom surface of the cushioning layer 26 as described herein. Asshown in the bottom view of the midsole system 318 in FIG. 20 (with thelayer 70 removed), each cushioning unit 19 is shown fluidly isolatedfrom each other cushioning unit. However, some or all of the cushioningunits may be interconnected by channels 43 and/or linking chambers, asdescribed herein.

The sole structure 312 includes an additional cushioning layer 70underlying the plurality of cushioning units 19. The additionalcushioning layer 70 may be another layer of the midsole system, or maybe an outsole, or a combination of a midsole layer and an outsole. Asshown, the cushioning layer 70 serves as an outsole, and forms theground contact surface 35. The additional cushioning layer 70 includes aplurality of stanchions 72 extending generally upward from a base 74 ofthe cushioning layer 70. The stanchions 72 are spaced apart from oneanother in correspondence with relative spacing of the cushioning units19 such that the stanchions 72 can interface with the cushioning units19 in a one-to-one ratio. Stated differently, the stanchions 72 arepaired with the cushioning units 19. Each stanchion 72 may be generallyround in cross-section perpendicular to its length. The center 72C ofeach stanchion may be hollowed out, as shown in FIG. 19 in order toreduce weight.

Each stanchion 72 interfaces with the domed lower surface 28 of arespective one of the plurality of cushioning units 19. Each stanchion72 has a concave upper surface 76 (also referred to herein as thestanchion interface area) that cups at least a portion of the domedlower surface 28 of the respective one of the plurality of cushioningunits 19. Under compressive loading of a cushioning unit 19, the domedlower surface 28 of the first cushioning layer 38 is compressed againstthe stanchion 72.

The stanchions 72 are configured to affect the cushioning response ofthe sole structure 312 as the foot strikes with an impact in the heelregion 17, and the wearer's weight moves forward from heel to toe. Forexample, the stanchions 72 decrease in height from the heel region tothe forefoot region, as shown in FIG. 18. In other words, the stanchions72 in the heel region 17 extend further from the base 74 than those inthe midfoot region 15 and the forefoot region 13. The stanchions 72 alsoincrease in width, at least in width relative to the width of theoverlying cushioning unit 19 or both, from the heel region 17 to theforefoot region 13. Generally, a narrower stanchion 72 relative to adomed lower surface 28 of a cushioning unit 19 will allow more of thefirst cushioning layer 38 to collapse over the stanchion 72 undercompressive loading, isolating loading to the first cushioning layer fora greater range of displacement (compression) than a wider stanchion.Assuming the first cushioning layer 38 is less stiff than the secondcushioning layer 40, a narrower stanchion relative to the domed lowersurface may provide a softer (less stiff) initial loading response.Similarly, a shorter stanchion 72, such as in the forefoot region 13,allows less displacement of the cushioning unit 19 prior to the domedlower surface 28 of the cushioning unit bottoming out relative to thestanchion, providing a stiffer initial loading response relative to ataller stanchion.

The interface area of the stanchion 72 (i.e., the surface 76 where itcontacts and cups the domed lower surface 28) to the total area of thedomed lower surface 28 governs how the first cushioning layer 22 candeform (compress). Generally, a larger ratio of the area of surface 76to the total area of the domed lower surface 28 (i.e., a larger ratio ofthe interface area to total area) results in a stiffer response of thecushioning unit 19 by minimizing the ability of the first cushioninglayer 22 to deform over the stanchion 72. In one or more embodiments, aratio of stanchion interface area 76 to total area of the domed lowersurface 28 for each of the plurality of cushioning units 19 may begreater on average for the forefoot cushioning units (i.e., the fourcushioning units 19 furthest to the right in FIG. 18) interfacing withthe forefoot stanchions 72 than for the heel cushioning unitsinterfacing with the heel stanchions 72. Accordingly, the less stifffirst cushioning layer 38 affects cushioning over a greater range ofdisplacement in the heel region 17 than in the forefoot region 13,providing a relatively stiffer response in the forefoot region, as isappropriate for supporting toe-off.

The increase in compressive force with vertical displacement of thesealed chambers 38 by the corresponding stanchions 72 (i.e., stiffness)in the heel region 17 is illustrated in FIG. 21, in the midfoot regionin FIG. 22, and in the forefoot region in FIG. 23. FIG. 21 illustratesthat the relatively tall stanchions and low ratio of interface area 76to total area of the cushioning unit 19 results in a relatively low,linear stiffness for a relatively large amount of vertical displacementin the heel region. The nonlinear portion of the curve in FIG. 21 beginswhen the cushioning units 19 bottom out against the base 74. FIG. 22illustrates that the somewhat shorter and wider stanchions 72 in themidfoot region 15 result in a quicker transition to a higher, nonlinearstiffness in the midfoot region 15 than in the heel region 17. FIG. 23illustrates that the nearly one-to-one ratio of the interface area 76and domed surface 28 results in a fast-loading, energy efficient linearstiffness greater than the stiffness of the linear portion of thestiffness in the heel region and midfoot region, as is appropriate fortoe-off. In a nonlimiting example, the stanchions 72 can be 10 mmdiameter at the rear of the heel region 17, while the cushioning units19 are 29 mm in diameter. The width of the stanchions gradually progressto 20 mm in the midfoot region 15, and then to 25 mm in the forefootregion 13. The cushioning units 19 may be smaller in diameter in theforefoot region 13, such as 25 mm to match the diameter of the overlyingcushioning unit 19 supported thereon.

FIG. 24 shows a sole layer 426 included in the sole structure 412 of thearticle of footwear 410 of FIGS. 25-26. The sole structure 412 comprisesa midsole system 418 having a bladder 431 comprising four stackedpolymeric sheets 432, 434, 436, 437 bonded to one another and defining afirst cushioning layer 422, a second cushioning layer 424, and a thirdcushioning layer (i.e., the sole layer 426), each cushioning layercomprising a sealed chamber retaining gas in isolation from each othersealed chamber. The four stacked polymeric sheets include a firstpolymeric sheet 432, a second polymeric sheet 434, a third polymericsheet 436, and a fourth polymeric sheet 437. The first cushioning layer422 is formed by the first and second polymeric sheets 432, 434, whichform and define a first sealed chamber 438 bounded by the firstpolymeric 432 and the second polymeric sheet 434. The second polymericsheet 434 and the third polymeric sheet 436 form and define a secondsealed chamber 440 bounded by the second polymeric sheet 434 and thethird polymeric sheet 436. The third cushioning layer 426 includes athird sealed chamber 441 that is formed, defined, and bounded by thethird polymeric sheet 436 and the fourth polymeric sheet 437. The first,second, third, and fourth polymeric sheets 432, 434, 436, and 437 are amaterial that is impervious to gas, such as air, nitrogen, or anothergas. This enables the first sealed chamber 438 to retain a gas at afirst predetermined pressure, the second sealed chamber 440 to retain agas at a second predetermined pressure, and the third sealed chamber 441to retain a gas at a third predetermined pressure.

The sole layer 426 overlies the bladder 431 and is configured with abottom surface 463 having an outer peripheral portion 464 and a centralportion 465 surrounded by the outer peripheral portion 464. As shown inFIG. 24, the outer peripheral portion 464 extends around the front, therear, the medial side, and the lateral side of the sole layer 426, andcompletely surrounds the central portion 465. The central portion 465 isrecessed in the bottom surface 463 further than the outer peripheralportion 464, such that a ridge 466 generally defines a boundary betweenthe portions 464, 465. An insole 421 overlies the sole layer 426, and afootwear upper 14 is secured to the sole structure 412.

As shown in FIG. 25, the outer peripheral portion 464 is mated with anupper surface 467 of bladder 431 in an unloaded state of the solestructure 412, and the central portion 465 is at least partially spacedapart from the upper surface 467 of the bladder 431 in the unloadedstate of the sole structure 412. Stated differently, the outerperipheral portion 464 of the surface 463 has a complete and constantinterface with the entire area of the outer peripheral portion of thebladder 431 (i.e., is geometrically “keyed” to the corresponding outerperipheral portion of the bladder 431), while the central portion 465 isnot keyed to the bladder. This configuration allows greater displacementof the bladder 431 relative to the central portion 465 than the outerperipheral portion 464 prior to compression of the bladder 431 under acompressive load on the sole structure 412. Compression of the outerperipheral portion 464, by contrast, begins immediately under acompressive load due to the keyed outer peripheral portion 464. Animmediate, relatively high stiffness may thus be achieved at the outerperipheral portion 464, in order to provide stability to counteract foottendencies for overpronation and supination.

Because the central portion 465 is not keyed to the bladder 431, one ormore gaps 469 exist between the top surface 471 of the bladder 431 andthe central portion 465 of the surface 463 of the sole layer 426. Thisallows some vertical displacement of the sole layer 426 and the bladder431 relative to one another under a compressive load, as shown in FIG.26. The central portion 465 may achieve a softer (less stiff) initialcushioning response as the sole structure 412 initially compresses untilthe top surface 471 of the bladder 431 conforms to the central portion465 of the bottom surface 463 of the sole layer 426 after the initialstage of compressive loading, presenting an initially soft ride (lowstiffness) to the overlying central portion of the foot.

The sole structure 412 also includes an underlying sole layer 420, suchas an outsole or an additional midsole layer, which underlies thebladder 431. In the embodiment shown, the sole layer 420 is an outsole.An upper surface 423 of the underlying sole layer is mated with a bottomsurface 428 of the bladder 431 in both the unloaded state and undercompressive loading of the sole structure 412.

FIG. 27 shows a midsole system 518 for a sole structure for an articleof footwear. The midsole system 518 has a first cushioning unit 519A anda second cushioning unit 519B. Each of the cushioning units 519A, 519Bis identical to the cushioning unit 19 shown and described with respectto FIG. 2, with the outsole 20 being optional. Moreover, each of thecushioning units is connected to other cushioning units. For example,the first cushioning unit 519A is connected to cushioning units 519C and519D, and may be in fluid communication with either of both ofcushioning units 519C, 519D. FIG. 27 is a fragmentary view of themidsole system 518, and other cushioning units may also be connected tocushioning unit 519A. The second cushioning unit 519B is connected tocushioning units 519E and 519F, and may be in fluid communication witheither of both of cushioning units 519E, 519F. FIG. 27 is a fragmentaryview of the midsole system 518, and other cushioning units may also beconnected to cushioning unit 519B.

As described with respect to cushioning unit 19, each cushioning unit519A, 519B includes a first, a second, and a third polymeric sheet,indicated as sheets 32A, 34A, and 36A for the first cushioning unit519A, and sheets 32B, 34B, and 36B for the second cushioning unit 519B.The first cushioning unit 519A comprises a first cushioning layer 22Athat includes a first sealed chamber 38A, and a second cushioning layer24A that includes a second sealed chamber 40A. The first sealed chamber38A and the second sealed chamber 40A each retain gas in isolation fromone another. The second cushioning unit 519B comprises a firstcushioning layer 22B that includes a first sealed chamber 38B, and asecond cushioning layer 24B that includes a second sealed chamber 40B.The first sealed chamber 38B and the second sealed chamber 40B eachretain gas in isolation from one another. As described herein withrespect to cushioning unit 19, the first cushioning layer 22A, 22B ofeach cushioning unit 519A, 519B has a domed surface 28A, 28B extendingaway from the respective second cushioning layer 24A, 24B, and thesecond cushioning layer 24A, 24B is annular and borders a centralportion of the first cushioning layer 22A, 22B.

The first cushioning unit 519A is inverted and the second cushioningunit 519B is stacked on the inverted first cushioning unit 519A suchthat the first cushioning layer 22A of the first cushioning unit 519Ainterfaces with and underlies the first cushioning layer 22B of thesecond cushioning unit 519B. More specifically, the domed surface 28A ofthe first cushioning unit 519A (now an upper surface, as the firstcushioning unit 519A is inverted) interfaces with the domed lowersurface 28B of the second cushioning unit 519B. The cushioning units519A, 519B are thus disposed in an inverted relationship to one another.The cushioning units 519C, 519E, and the cushioning units 519D and 519Finterface in a like manner. In embodiments in which the first cushioninglayers 22A, 22B are less stiff than the second cushioning layers 24A,24B, such as when the pressure of the gas in the first sealed chambers38A, 38B of the respective first cushioning layers 22A, 22B are lessthan the pressure of the gas in the second sealed chambers 40A, 40B ofthe respective second cushioning layers 24A, 24B in an unloaded state ofthe midsole system 518, stacking the cushioning units 519A, 519B so thatthe least stiff first cushioning layers 22A, 22B interface with oneanother will effectively allow a greater range of displacement of thesole structure in an initial (first) stage of compression that isaffected only by the least stiff first cushioning layers 22A, 22B thanif a stiffer layer were disposed vertically between the first cushioninglayers 22A, 22B.

FIG. 28 shows another embodiment of a midsole system 618 for a solestructure for an article of footwear with vertically stacked cushioningunits. The midsole system 618 has a first cushioning unit 619A and asecond cushioning unit 619B. Each of the cushioning units 619A, 619B hasfour polymeric sheets, three cushioning layers, and three sealedchambers, constructed identically to those of the bladder 431 shown anddescribed with respect to FIG. 25. More specifically, each cushioninglayer 619A and 619B includes the four stacked polymeric sheets. The fourstacked polymeric sheets 432A, 434A, 436A, 437A of the first cushioningunit 619A are bonded to one another and defining a first cushioninglayer 422A, a second cushioning layer 424A, and a third cushioning layer426A, each cushioning layer comprising a sealed chamber 438A, 440A,441A, respectively, retaining gas in isolation from each other sealedchamber. The four stacked polymeric sheets 432B, 434B, 436B, 437B of thesecond cushioning unit 619B are bonded to one another and defining afirst cushioning layer 422B, a second cushioning layer 424B, and a thirdcushioning layer 426B, each cushioning layer comprising a sealed chamber438B, 440B, 441B, respectively, retaining gas in isolation from eachother sealed chamber. FIG. 28 is a fragmentary view of the midsolesystem 618.

The first cushioning unit 619A is inverted and the second cushioningunit 619B is stacked on the inverted first cushioning unit 619A suchthat the first cushioning layer 422A of the first cushioning unit 619Ainterfaces with and underlies the first cushioning layer 422B of thesecond cushioning unit 619B. More specifically, the surface 428A of thefirst cushioning unit 619A interfaces with the surface 428B of thesecond cushioning unit 619B. The cushioning units 619A, 619B are thusdisposed in an inverted relationship to one another. In embodiments inwhich the first cushioning layers 422A, 422B are less stiff than thesecond cushioning layers 424A, 424B, such as when the pressure of thegas in the first sealed chamber 438A, 438B of the respective firstcushioning layer 422A, 422B is less than the pressure of the gas in therespective second sealed chamber 440A, 440B of the second cushioninglayers 424A, 424B in an unloaded state of the midsole system 618,stacking the cushioning units 519A, 519B so that the least stiff firstcushioning layers 422A, 422B interface with one another will effectivelyallow a greater range of displacement of the midsole system 618 in aninitial (first) stage of compression that is affected only by the leaststiff first cushioning layers 422A, 422B than if a stiffer layer weredisposed vertically between the first cushioning layers 422A, 422B.

FIGS. 29-31 show polymeric sheets 732, 734, 736 with patterns ofanti-weld material 711 disposed on the sheets. The pattern 711A isdisposed on the top surface of the first sheet 732. The pattern 711B isdisposed on both upper and lower surfaces of the second sheet 734. Thepattern 711C is disposed on the lower surface of the third sheet 736. Ifthe sheets are then stacked in order of sheets 732, 734, 736, with sheet732 at the bottom, the sheets 732, 734, 736 will bond to one another inall adjacent surfaces not covered with the anti-weld material 711. Thepatterns 711A, 711B, 711C will result in a series of the cushioningunits 19 with the domed lower surfaces 28. The channels 43 on the lowersheet 732 indicate that the first chambers 38 of the resultingcushioning units 19 will be in fluid communication. The channels 43 onthe third sheet 736 indicate that the second chambers 40 of theresulting cushioning units will be in fluid communication. Only some ofthe channels 43 are labeled in the drawings.

In one non-limiting example, the various embodiments of midsolesdisclosed herein may provide energy return from about 59% to about 82%,when energy return is measured as the percent restoration of initialdrop height of an impact tester, or is measured with a mechanical testersuch as an INSTRON® tester available from Instron Corporation, NorwoodMass.

To assist and clarify the description of various embodiments, variousterms are defined herein. Unless otherwise indicated, the followingdefinitions apply throughout this specification (including the claims).Additionally, all references referred to are incorporated herein intheir entirety.

An “article of footwear”, a “footwear article of manufacture”, and“footwear” may be considered to be both a machine and a manufacture.Assembled, ready to wear footwear articles (e.g., shoes, sandals, boots,etc.), as well as discrete components of footwear articles (such as amidsole, an outsole, an upper component, etc.) prior to final assemblyinto ready to wear footwear articles, are considered and alternativelyreferred to herein in either the singular or plural as “article(s) offootwear” or “footwear”.

“A”, “an”, “the”, “at least one”, and “one or more” are usedinterchangeably to indicate that at least one of the items is present. Aplurality of such items may be present unless the context clearlyindicates otherwise. All numerical values of parameters (e.g., ofquantities or conditions) in this specification, unless otherwiseindicated expressly or clearly in view of the context, including theappended claims, are to be understood as being modified in all instancesby the term “about” whether or not “about” actually appears before thenumerical value. “About” indicates that the stated numerical valueallows some slight imprecision (with some approach to exactness in thevalue; approximately or reasonably close to the value; nearly). If theimprecision provided by “about” is not otherwise understood in the artwith this ordinary meaning, then “about” as used herein indicates atleast variations that may arise from ordinary methods of measuring andusing such parameters. As used in the description and the accompanyingclaims, unless stated otherwise, a value is considered to be“approximately” equal to a stated value if it is neither more than 5percent greater than nor more than 5 percent less than the stated value.In addition, a disclosure of a range is to be understood as specificallydisclosing all values and further divided ranges within the range.

The terms “comprising”, “including”, and “having” are inclusive andtherefore specify the presence of stated features, steps, operations,elements, or components, but do not preclude the presence or addition ofone or more other features, steps, operations, elements, or components.Orders of steps, processes, and operations may be altered when possible,and additional or alternative steps may be employed. As used in thisspecification, the term “or” includes any one and all combinations ofthe associated listed items. The term “any of” is understood to includeany possible combination of referenced items, including “any one of” thereferenced items. The term “any of” is understood to include anypossible combination of referenced claims of the appended claims,including “any one of” the referenced claims.

For consistency and convenience, directional adjectives may be employedthroughout this detailed description corresponding to the illustratedembodiments. Those having ordinary skill in the art will recognize thatterms such as “above”, “below”, “upward”, “downward”, “top”, “bottom”,etc., may be used descriptively relative to the figures, withoutrepresenting limitations on the scope of the invention, as defined bythe claims.

The term “longitudinal” refers to a direction extending a length of acomponent. For example, a longitudinal direction of an article offootwear extends between a forefoot region and a heel region of thearticle of footwear. The term “forward” or “anterior” is used to referto the general direction from a heel region toward a forefoot region,and the term “rearward” or “posterior” is used to refer to the oppositedirection, i.e., the direction from the forefoot region toward the heelregion. In some cases, a component may be identified with a longitudinalaxis as well as a forward and rearward longitudinal direction along thataxis. The longitudinal direction or axis may also be referred to as ananterior-posterior direction or axis.

The term “transverse” refers to a direction extending a width of acomponent. For example, a transverse direction of an article of footwearextends between a lateral side and a medial side of the article offootwear. The transverse direction or axis may also be referred to as alateral direction or axis or a mediolateral direction or axis.

The term “vertical” refers to a direction generally perpendicular toboth the lateral and longitudinal directions. For example, in caseswhere a sole structure is planted flat on a ground surface, the verticaldirection may extend from the ground surface upward. It will beunderstood that each of these directional adjectives may be applied toindividual components of a sole structure. The term “upward” or“upwards” refers to the vertical direction pointing towards a top of thecomponent, which may include an instep, a fastening region and/or athroat of an upper. The term “downward” or “downwards” refers to thevertical direction pointing opposite the upwards direction, toward thebottom of a component and may generally point towards the bottom of asole structure of an article of footwear.

The “interior” of an article of footwear, such as a shoe, refers toportions at the space that is occupied by a wearer's foot when thearticle of footwear is worn. The “inner side” of a component refers tothe side or surface of the component that is (or will be) orientedtoward the interior of the component or article of footwear in anassembled article of footwear. The “outer side” or “exterior” of acomponent refers to the side or surface of the component that is (orwill be) oriented away from the interior of the article of footwear inan assembled article of footwear. In some cases, other components may bebetween the inner side of a component and the interior in the assembledarticle of footwear. Similarly, other components may be between an outerside of a component and the space external to the assembled article offootwear. Further, the terms “inward” and “inwardly” refer to thedirection toward the interior of the component or article of footwear,such as a shoe, and the terms “outward” and “outwardly” refer to thedirection toward the exterior of the component or article of footwear,such as the shoe. In addition, the term “proximal” refers to a directionthat is nearer a center of a footwear component, or is closer toward afoot when the foot is inserted in the article of footwear as it is wornby a user. Likewise, the term “distal” refers to a relative positionthat is further away from a center of the footwear component or isfurther from a foot when the foot is inserted in the article of footwearas it is worn by a user. Thus, the terms proximal and distal may beunderstood to provide generally opposing terms to describe relativespatial positions.

While various embodiments have been described, the description isintended to be exemplary, rather than limiting and it will be apparentto those of ordinary skill in the art that many more embodiments andimplementations are possible that are within the scope of theembodiments. Any feature of any embodiment may be used in combinationwith or substituted for any other feature or element in any otherembodiment unless specifically restricted. Accordingly, the embodimentsare not to be restricted except in light of the attached claims andtheir equivalents. Also, various modifications and changes may be madewithin the scope of the attached claims.

While several modes for carrying out the many aspects of the presentteachings have been described in detail, those familiar with the art towhich these teachings relate will recognize various alternative aspectsfor practicing the present teachings that are within the scope of theappended claims. It is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and exemplary of the entire range of alternativeembodiments that an ordinarily skilled artisan would recognize asimplied by, structurally and/or functionally equivalent to, or otherwiserendered obvious based upon the included content, and not as limitedsolely to those explicitly depicted and/or described embodiments.

What is claimed is:
 1. A sole structure for an article of footwearcomprising: a midsole system including a plurality of cushioning units,each cushioning unit including: a first cushioning layer comprising afirst sealed chamber; and a second cushioning layer comprising a secondsealed chamber, the first sealed chamber and the second sealed chambereach retaining gas in isolation from one another; wherein the firstcushioning layer underlies the second cushioning layer and has a domedlower surface extending away from the second cushioning layer; andwherein the second cushioning layer is annular and borders a centralportion of the first cushioning layer above the domed lower surface. 2.The sole structure of claim 1, wherein the plurality of cushioning unitsinclude interconnected cushioning units having fluid communicationbetween the second sealed chamber of each of the interconnectedcushioning units.
 3. The sole structure of claim 2, wherein: the midsolesystem comprises a linking chamber; and at least some of theinterconnected cushioning units laterally surround the linking chamber,with the second sealed chamber of each laterally-surroundinginterconnected cushioning unit in fluid communication with the linkingchamber.
 4. The sole structure of claim 2, wherein: the sole structurehas a heel region, a forefoot region, and a midfoot region between theheel region and the forefoot region; and the interconnected cushioningunits are disposed in the forefoot region.
 5. The sole structure ofclaim 4, wherein: the interconnected cushioning units in the forefootregion are a first group of interconnected cushioning units; theplurality of cushioning units includes a second group of interconnectedcushioning units having fluid communication between the second sealedchamber of each of the interconnected cushioning units of the secondgroup; and the second group are disposed in the heel region and themidfoot region and is fluidly-isolated from the first group.
 6. The solestructure of claim 5, wherein the second group of interconnectedcushioning units are arranged in a serpentine shape.
 7. The solestructure of claim 2, wherein: the sole structure has a heel region, aforefoot region, and a midfoot region between the heel region and theforefoot region; the interconnected cushioning units are disposed in theheel region and the midfoot region and are arranged in a serpentineshape.
 8. The sole structure of claim 2, wherein: the sole structure hasa periphery; the plurality of cushioning units includes multipleisolated cushioning units each fluidly-isolated from all other ones ofthe plurality of cushioning units; and the multiple isolated cushioningunits are disposed between the periphery and the interconnectedcushioning units.
 9. The sole structure of claim 1, wherein: theplurality of cushioning units include multiple isolated cushioning unitseach disposed adjacent a periphery of the sole structure, and eachfluidly-isolated from all other ones of the plurality of cushioningunits.
 10. The sole structure of claim 1, wherein: the midsole systemcomprises a first polymeric sheet, a second polymeric sheet, and a thirdpolymeric sheet; the first polymeric sheet and the second polymericsheet define the first sealed chamber of each of the plurality ofcushioning units, the first polymeric sheet defines the domed lowersurface of each of the plurality of cushioning units, the secondpolymeric sheet and the third polymeric sheet define the second sealedchamber of each of the plurality of cushioning units, the secondpolymeric sheet and the third polymeric sheet are bonded to one anotherat bonds each of which extends over the central portion of the firstsealed chamber of a respective one of the plurality of cushioning unitsand is bordered by the second sealed chamber of the respective one ofthe plurality of cushioning units.
 11. The sole structure of claim 1,wherein: the midsole system further comprises a third cushioning layeroverlying the plurality of cushioning units; and a lower surface of thethird cushioning layer has a plurality of recesses shaped such that theplurality of cushioning units are nested in the third cushioning layerat the plurality of recesses.
 12. The sole structure of claim 1, furthercomprising: an additional cushioning layer underlying the plurality ofcushioning units; wherein the additional cushioning layer includes aplurality of stanchions; and wherein each stanchion interfaces with thedomed lower surface of a respective one of the plurality of cushioningunits.
 13. The sole structure of claim 12, wherein: at least some of theplurality of stanchions have concave upper surfaces each of which cupsat least a portion of the domed lower surface of the respective one ofthe plurality of cushioning units.
 14. The sole structure of claim 12,wherein: the sole structure has a heel region, a forefoot region, and amidfoot region between the heel region and the forefoot region; and theplurality of stanchions decrease in height, increase in width, or both,from the heel region to the forefoot region.
 15. The sole structure ofclaim 12, wherein: a ratio of stanchion interface area to total area ofthe domed lower surface for each of the plurality of cushioning units isgreater on average for the forefoot cushioning units interfacing withthe forefoot stanchions than for the heel cushioning units interfacingwith the heel stanchions.
 16. A sole structure for an article offootwear comprising: a midsole system having: a bladder comprising fourstacked polymeric sheets bonded to one another and defining a firstcushioning layer, a second cushioning layer, and a third cushioninglayer, each cushioning layer comprising a sealed chamber retaining gasin isolation from each other sealed chamber; a sole layer overlying thebladder and configured with a bottom surface having an outer peripheralportion and a central portion surrounded by the outer peripheralportion; wherein the outer peripheral portion is mated with an uppersurface of bladder in an unloaded state of the sole structure, and thecentral portion is at least partially spaced apart from the uppersurface of the bladder in the unloaded state of the sole structure. 17.The sole structure of claim 16, wherein the bladder conforms to thecentral portion of the bottom surface of the sole layer undercompressive loading; and the sole structure further comprising: anadditional sole layer underlying the bladder; wherein an upper surfaceof the additional sole layer is mated with a bottom surface of thebladder in both the unloaded state and under compressive loading of thesole structure.
 18. A sole structure for an article of footwearcomprising: a midsole system having a first cushioning unit and a secondcushioning unit, each cushioning unit including: a first cushioninglayer comprising a first sealed chamber; and a second cushioning layercomprising a second sealed chamber, the first sealed chamber and thesecond sealed chamber each retaining gas in isolation from one another;wherein the first cushioning unit is inverted and the second cushioningunit is stacked on the first cushioning unit such that the firstcushioning layer of the first cushioning unit interfaces with andunderlies the first cushioning layer of the second cushioning unit. 19.The sole structure of claim 18, wherein: the first cushioning layer ofeach cushioning unit has a domed surface extending away from the secondcushioning layer, and the second cushioning layer is annular and bordersa central portion of the first cushioning layer; and the domed surfaceof the first cushioning unit interfaces with the domed surface of thesecond cushioning unit.
 20. The sole structure of claim 18, wherein:each cushioning unit has four stacked polymeric sheets bonded to oneanother to define the first sealed chamber bounded by the firstpolymeric sheet and the second polymeric sheet, the second sealedchamber bounded by the second polymeric sheet and the third polymericsheet, and a third sealed chamber bounded by the third polymeric sheetand the fourth polymeric sheet.